﻿using System;
using System.Collections.Generic;
using System.Text;

namespace StationUpdate
{
    public class Crc16
    {
        //public Crc16() { }

        private readonly int[] crc16_table =
     {
	    0x0000,0xC0C1,0xC181,0x0140,0xC301,0x03C0,0x0280,0xC241,
		0xC601,0x06C0,0x0780,0xC741,0x0500,0xC5C1,0xC481,0x0440,
		0xCC01,0x0CC0,0x0D80,0xCD41,0x0F00,0xCFC1,0xCE81,0x0E40,
		0x0A00,0xCAC1,0xCB81,0x0B40,0xC901,0x09C0,0x0880,0xC841,
		0xD801,0x18C0,0x1980,0xD941,0x1B00,0xDBC1,0xDA81,0x1A40,
		0x1E00,0xDEC1,0xDF81,0x1F40,0xDD01,0x1DC0,0x1C80,0xDC41,
		0x1400,0xD4C1,0xD581,0x1540,0xD701,0x17C0,0x1680,0xD641,
		0xD201,0x12C0,0x1380,0xD341,0x1100,0xD1C1,0xD081,0x1040,
		0xF001,0x30C0,0x3180,0xF141,0x3300,0xF3C1,0xF281,0x3240,
		0x3600,0xF6C1,0xF781,0x3740,0xF501,0x35C0,0x3480,0xF441,
		0x3C00,0xFCC1,0xFD81,0x3D40,0xFF01,0x3FC0,0x3E80,0xFE41,
		0xFA01,0x3AC0,0x3B80,0xFB41,0x3900,0xF9C1,0xF881,0x3840,
		0x2800,0xE8C1,0xE981,0x2940,0xEB01,0x2BC0,0x2A80,0xEA41,
		0xEE01,0x2EC0,0x2F80,0xEF41,0x2D00,0xEDC1,0xEC81,0x2C40,
		0xE401,0x24C0,0x2580,0xE541,0x2700,0xE7C1,0xE681,0x2640,
		0x2200,0xE2C1,0xE381,0x2340,0xE101,0x21C0,0x2080,0xE041,
		0xA001,0x60C0,0x6180,0xA141,0x6300,0xA3C1,0xA281,0x6240,
		0x6600,0xA6C1,0xA781,0x6740,0xA501,0x65C0,0x6480,0xA441,
		0x6C00,0xACC1,0xAD81,0x6D40,0xAF01,0x6FC0,0x6E80,0xAE41,
		0xAA01,0x6AC0,0x6B80,0xAB41,0x6900,0xA9C1,0xA881,0x6840,
		0x7800,0xB8C1,0xB981,0x7940,0xBB01,0x7BC0,0x7A80,0xBA41,
		0xBE01,0x7EC0,0x7F80,0xBF41,0x7D00,0xBDC1,0xBC81,0x7C40,
		0xB401,0x74C0,0x7580,0xB541,0x7700,0xB7C1,0xB681,0x7640,
		0x7200,0xB2C1,0xB381,0x7340,0xB101,0x71C0,0x7080,0xB041,
		0x5000,0x90C1,0x9181,0x5140,0x9301,0x53C0,0x5280,0x9241,
		0x9601,0x56C0,0x5780,0x9741,0x5500,0x95C1,0x9481,0x5440,
		0x9C01,0x5CC0,0x5D80,0x9D41,0x5F00,0x9FC1,0x9E81,0x5E40,
		0x5A00,0x9AC1,0x9B81,0x5B40,0x9901,0x59C0,0x5880,0x9841,
		0x8801,0x48C0,0x4980,0x8941,0x4B00,0x8BC1,0x8A81,0x4A40,
		0x4E00,0x8EC1,0x8F81,0x4F40,0x8D01,0x4DC0,0x4C80,0x8C41,
		0x4400,0x84C1,0x8581,0x4540,0x8701,0x47C0,0x4680,0x8641,
		0x8201,0x42C0,0x4380,0x8341,0x4100,0x81C1,0x8081,0x4040
};

        public  ushort getCrc16(string strAllBusData)
        {

            char[] chars = strAllBusData.ToCharArray();
            int ncharlen = chars.Length;
            int nCountOfNull = 0;
            ushort res = 0;
            for (int n = 0; n < ncharlen; n++)
            {
                if (chars[0] != 0)
                {
                    res = 0x0000;
                    for (n = nCountOfNull; n < ncharlen - nCountOfNull; n++, n++)
                    {
                        char szTemp = '\0', _szTemp1 = '\0', _szTemp2 = '\0', _szTemp3 = '\0';
                        szTemp = chars[n];
                        if (szTemp >= '0' && szTemp <= '9')
                        {
                            _szTemp1 = (char)((int)szTemp - 0x30);
                        }
                        if (szTemp >= 'A' && szTemp <= 'F')
                        {
                            _szTemp1 = (char)((int)szTemp - 0x37);
                        }
                        if (szTemp >= 'a' && szTemp <= 'f')
                        {
                            _szTemp1 = (char)((int)szTemp - 0x57);
                        }


                        szTemp = chars[n + 1];
                        if (szTemp >= '0' && szTemp <= '9')
                        {
                            _szTemp2 = (char)((int)szTemp - 0x30);
                        }
                        if (szTemp >= 'A' && szTemp <= 'F')
                        {
                            _szTemp2 = (char)((int)szTemp - 0x37);
                        }
                        if (szTemp >= 'a' && szTemp <= 'f')
                        {
                            _szTemp2 = (char)((int)szTemp - 0x57);
                        }

                        _szTemp3 = (char)(((int)_szTemp1) * 0x10 + (int)_szTemp2);

                        ushort v;
                        v = (ushort)((res & 0xff) ^ ((ushort)_szTemp3 & 0xff));
                        res = (ushort)(((res >> 8) & 0xff) ^ crc16_table[v]);
                    }

                    res = (ushort)(res << 8 & 0xff00 | res >> 8 & 0x00ff);
                    return res;

                }
                else
                {
                    nCountOfNull++;
                }
            }

            return res;
        }
    }
}
